The present invention relates to a power transmission apparatus.
Conventional power transmission apparatuses have been known, which transmit drive force inputted from a driving source to two output shafts using a differential mechanism and distribute the drive force into the two output shafts by linking the input shaft to one of the output shafts using a clutch mechanism.
The power transmission apparatus described in Japanese Laid-Open Patent Publication No. 9-144845, for example, is provided with a differential case which is rotated by drive force from a driving source and a differential mechanism that is contained within the differential case. The differential mechanism is provided with a sun gear, an internal gear and a pinion gear. The sun gear and the internal gear are contained within the differential case so as to be freely rotatable. The pinion gear is contained in a accommodation hole within the differential gear so as to be freely rotatable in an engaged state with the sun gear and the internal gear. In the apparatus described in this document, the pinion gear is contained in the accommodation hole within the differential case so as to be freely rotatable, and therefore, a carrier for supporting the pinion gear can be omitted, so that a space can accordingly be created in a location adjacent to the pinion gear. A clutch mechanism for linking the sun gear and the internal gear is provided in this space, and thus, reduction in the number of parts, miniaturization and reduction in weight can be achieved.
However, the space that is created by omitting the carrier, that is to say, the space between the sun gear and the internal gear, is extremely small. In this case, the volume of the clutch that is placed in the space between the sun gear and the internal gear is limited, and therefore, it is difficult to transmit greater torque to this clutch. Therefore, in the case of the conventional apparatus, it is necessary to increase the space between the sun gear and the internal gear in the axial direction, so that the space can accommodate a clutch having a large capacity for transmitting greater torque. Thus, the apparatus inevitably becomes long in the axial direction, which causes a problem such that the length in the axial direction and the weight of the transfer (or differential) for containing this apparatus increase.